Radio systems have long been used to provide trunk connections in the telecommunications network. Recently, radio systems have been devised for local distribution applications, especially in the urban environment, which supply high-capacity communications channels and can provide for new wideband services, such as video teleconferencing. While coaxial and optical fiber communications systems can also be used for such applications, the installation of cable ducts is expensive, can take years to construct and can be disruptive in a city environment. Radio systems, on the other hand, can often be more readily installed and can provide the high information carrying capacities and bandwidths required for expanding communications needs.
A variety of terrestrial radio systems for local distribution network applications have been proposed. See, for example, publications entitled "A cost-effective 19 GHz digital multipoint radio system for local distribution applications", by M. T. H. Hewitt et al., British Telecom. Technol. Journal, Vol. 2, No. 4, September 1984, pp. 94-101, and "29 GHz point-to-point radio systems for local distribution", by S. A. Mohamed and M. Pilgrim, British Telecom. Technol. Journal, Vol. 2, No. 1, January 1984, pp. 29-40. While these systems, designed for the urban environment, can provide the quick provision of broadband service in the local distribution network, they cannot accommodate the large number of system customers required in certain system applications, nor can they provide interference-free contiguous coverage. In addition, they cannot provide adequate fade margins over all portions of the available radio spectrum. Finally, for many intra-city applications, they cannot provide the very high system capacities required to satisfy the overall traffic demand.